1. Field of the Invention
The present invention relates to a manufacturing method of a substrate for an ink jet head that discharges ink for performing recording onto a recording medium in accordance with an ink jet system, and a manufacturing method of an ink jet head.
2. Related Background Art
There has conventionally been known an ink jet head (hereinafter referred to as “side shooter type head”) that discharges ink to the portion above an ink discharge pressure generating element. In this type of ink jet head, a through hole (ink supply opening) is formed on a substrate having a discharge energy generating section formed thereto, wherein ink is supplied from the back surface opposite to the surface on which the discharge energy generating section is provided.
U.S. Pat. No. 6,143,190 discloses a manufacturing method of this type of ink jet head. It discloses the manufacturing method including the steps described below in order to prevent the variation of the opening size of the through hole (ink supply opening). (a) a step of forming a sacrifice layer on the surface of the substrate at a location where the through hole is formed, wherein the sacrifice layer is capable of being selectively etched with respect to the material of the substrate; (b) a step of forming a passivation layer having resistance to an etching process on the substrate such that the sacrifice layer is covered with the passivation layer; (c) a step of forming an etching mask layer on the back surface of the substrate, the etching mask layer having an opening corresponding to the sacrifice layer; (d) a step of etching the substrate by means of a crystal axis anisotropic etching process until the sacrifice layer is exposed via the opening; (e) a step of removing the sacrifice layer by etching the sacrifice layer from the part which has been exposed in the step of etching the substrate; (f) a step of partially removing the passivation layer so as to form a through hole.
U.S. Pat. No. 6,107,209 discloses an anisotropic etching for Si material (Si substrate) having <100> crystal plane orientation. This Si anisotropic etching is characterized in that the Si material is heated beforehand, and then, etched, so as to form a processed section having “< >” shape.
U.S. Pat. No. 6,805,432 discloses a method of manufacturing an ink jet recording head in which a dry etching is performed by utilizing a mask provided at the back surface of a substrate, and then, a crystal axis anisotropic etching process is performed by using the same mask. The processed section having “< >” shape is also formed in accordance with this manufacturing method.
The manufacturing method for forming the processed section having “< >” shape has an advantage in that it can further downsize an element substrate of an ink jet recording head. Specifically, it is advantageous in that the width of the substrate can be reduced. A further miniaturization of a substrate described above has especially been demanded in a head having plural ink supply openings on a single substrate, such as a recording head for discharging color ink.
However, the method disclosed in U.S. Pat. No. 6,107,209 has a limitation on the distance from the bottom surface of the substrate to the bent portion of the “< >” shape. Further, the final shape varies depending upon the oxygen concentration in the silicon substrate, whereby it is difficult to achieve a stable manufacture.
On the other hand, in the method disclosed in U.S. Pat. No. 6,805,432, the mask for the wet etching is also used as the mask for the dry etching. In this method, the width of the opening of the ink supply opening is determined by the width of the opening of the mask at the back surface of the substrate and etching amount of the dry etching. Therefore, in order to reduce the width of the opening of the ink supply opening so as to form a so-called narrow supply opening, it is necessary to increase the etching amount in the dry etching. However, since it takes much time to etch by the dry etching, the problem of poor production efficiency arises.